| OCR Text |
Show 88 6, by some geologists. It appears in this horizon wherever access is obtained, but i » generally impure atfd of little or no value. Ten miles sonth of this point the following section exhibits it, ( Fig. 13.) The beds differ in thickness at different localities; their FIG. 13.- Hogback and lignite of Cretaceous Nos. 3 and 4 at Cristone, looking south. combined mass, with rather thin layers of slate, at one point reaching 50 feet. At the " locality of Fig. 13, it is overlaid by a heavy bed of yellow sandstone, from which I obtained teeth of sharks of the species Oxyrhinat and Galeocerdo pristodontus, Agass. These yellow beds are traversed for a mile to two miles west of the hog- back of Cretaceous No. 3, forming lines of low hills, from which I obtained numerous fossil Mollusca. These include Baculites, Ammonites of two species, including A. placenta, Inoccramwt, and a number of well- preservedDimyaria and Gastropida, On this account, 1 suppose these beds to represent Cretaceous No. 4. A portion of their lowest member lies on the hard portion of No. 3 at some points,, as already stated, forming the upper part of the hog- back; at least, I obtained the Baculites, an Ammonite, and the usual form of Inoceramue from such a locality. The two horizons are separated by the lignite, and, when this is eroded, a double line of hogbacks as in Plate IV. This sketch was taken from the southern extremity of the hogback of No. 3, of which the northern extremity is represented in the left- hand ledge of Fig. 13. The direction of view is to the southward. A hog- back of No. 4 is seen on the rignt, and the double hog- back, chiefly of No. 3, is in front of the observer. To the left horizon appear the southwestern slopes of the Nacimiento Mountain. The right horizon is occupied by the horizontal beds of the Eocene, and an arroyo which drains their slope pursues its way into the Gallinas Creek, which comes into view from the left hand. Immediately in front of its valley is a lower hill of Cretaceous No. 3, on whose summit stands a large stone building, one of the many which strew the crests of all these hog- backs. An account of these is given in my report on archeology. Further observations on the Cretaceous beds are deferred until the Eocene deposits are considered. CHAPTER VI. THE EOCENE PLATEAU. West of the hog- back of Cretaceous No. 3, at an interval of perhaps two miles, at a point just north of the Gallinas Mountain, a sandstone bluff presents a bold escarpment to the northeast. This is the angle of a mass of rock whose eastern face extends southward parallel to the mountain- axis, and whose strata dip first 15° then 10° south, and soon disappear beneath a similar mass. This series also presents an escarpment to the northeast, and its beds also dip 10° south, nearly opposite the canon of the Gallinas* This facade rises to from 600 to 900 feet elevation, and is cleft to the base by a deep gorge, the Caftonclta de las Vegas. I traversed this fissure, passing entirely through to the elevated country to the westward. Six miles from its month is a large pool, led by a spring known as the Mare's Spring. The canon is narrow, and the walls almost perpendicular. They are composed of tne " puerta," or entrance,. of a moderately hard, reddish- brown sandstone. The cafion is twenty miles in length,' its bottom has a gentle rise; and as the sandstone has a gentle dip toward the west as well as south, its upper beds reach the level of the bottom at about the middle of the length of the canon. Above them softer beds appear, alternating with strata of sandstone; the beds are first gray, but others soon appear which are striped with red. The red- striped marls increase in relative thickness toward the west, and the sandstone strata diminish until at the head of the cafion the high lands fall off in masses of hills of bright- colored marls eroded into rounded and picturesquely- formed hills. These extend in a long line to the |
